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The knee joint is a large weight-bearing joint consisting of the lower end of the femur (thigh bone), the upper end of the tibia (shin bone), and the patella (knee-cap).
The ends of these bones are covered with a thin layer of cartilage (gristle) called Articular Cartilage. It is similar to the white shiny surface you may have seen when you open up a chicken leg joint. The articular cartilage is very slippery and also acts like a cushion against shocks. This articular cartilage is only 2-3mm thick.
Arthritis of the knee is a result of wearing away of this special articular cartilage, exposing the bone underneath and leading to pain, stiffness, swelling and difficulty with walking and other weight bearing activities.
Knee arthritis can be a result of genetic reasons, inflammatory disease, aging, injury and being overweight.
In the early stages of the disease, symptoms are intermittent and fluctuate from day to day. They may even be periods of several weeks or months free of pain. Patients may experience pain and stiffness in the knee for the first few steps when they first stand up after sitting for some time. Once they start moving, they can still walk a good distance with pain only at the end of the day or after prolonged standing and walking.
As the disease progresses pain is experienced on most days, and the knee function deteriorates with limitation on walking, standing, kneeling and stair climbing. In severe cases, there may be pain at rest, at night and with most activities of daily living.
Although arthritis is a degenerative condition with deterioration of symptoms over time, the speed of progression of knee arthritis varies greatly between individuals. Many patients can cope with their arthritis for many years until something triggers an aggravation of their condition, after which they can no longer cope with the pain and disability.
The worn out articular cartilage in arthritis cannot be restored by current treatments, and therefore the disease is not reversible. However in early stages, symptoms may be controlled with non-surgical measures such as oral analgesics, anti-inflammatory medications, activity modification, non weight bearing exercise (e.g. swimming) and weight loss (when required).
Knee replacement surgery can be recommended in patients where symptoms significantly affect the quality of life.
The decision for knee replacement surgery is very individual and is best determined after consultation with your surgeon, who will assess factors such as your age, general health, your expectations, the severity of your symptoms, the findings on examining your knee, and the results of x-rays and other tests.
A successful knee replacement requires:
There are two common types of knee prostheses or implants:
Uni-compartmental Knee Replacement (UKR) – this is where only one half (the diseased half of the knee- usually the inside half) is replaced. This allows a slightly smaller incision, removal of less bone, less blood loss, a slightly quicker recovery and slightly greater amount of bend of the knee in the longer term. However, there are some disadvantages of uni-compartmental knee replacements.
Firstly, UKRs are very sensitive to small inconsistencies in the surgical technique i.e. minor errors in the surgical technique can mean the difference between success and failure of a UKR.
Secondly, determining the suitability of a patient for UKR is critical and there are many factors to take into account in that process. These include, type of arthritis, severity of arthritis, location of the arthritis in the knee, age, weight, and condition of the ligaments. Perhaps only 10% of patients who need knee replacement surgery may be suitable for UKR. If UKR is performed on an unsuitable patient, it may lead to a poor result. For these reasons, the pain relief after a UKR is not as predictable or consistent when compared to a total knee replacement (TKR).
Thirdly, it has been shown in many studies that UKR’s tend not to be as durable or long lasting compared to total knee replacements. In other words, UKR’s tend not to last as long as total knee replacements before they have to be re-operated or revised (the medical term for re-doing an operation) some years later.
According to the National Joint Replacement Registry (an Australian Government funded register that records every knee replacement that is performed in Australia), 15.3% of UKRs had been revised after 10 years compared to 5.6% for TKRs for the same period. In simple terms, if one hundred patients had a UKR, 15 of these have had required revision surgery by the time 10 year mark is reached.
There are two main reasons for which UKRs need to be revised. First reason is when the prosthesis loosens or “comes away” from the bone to which it was initially attached (using a special type of acrylic bone cement). This loosening tends to occur more frequently in UKR’s compared to TKRs as the surface area of bone to which the prosthesis is attached is smaller than in a TKR. The second reason for which UKRs are commonly revised is that the patient develops arthritis in the remaining half of the knee that was not replaced in a UKR.
Total Knee Replacement Surgery (TKR) – this is more commonly performed and the preferred operation for most cases of knee arthritis, as it relieves arthritic pain more predictably and tends to be more durable compared to uni-compartmental knee replacement.
The surgeon will decide on an individual basis, the suitability for the type of knee replacement surgery.
The rest of this discussion will refer to Total Knee Replacement (TKR) surgery.
The following is brief summary of the main steps in a total knee replacement.
An incision is made on the front of the knee to open up the joint. Diseased bone and cartilage are removed.
Using special aligning tools, the surgeon initially sets up jigs that are temporarily fixed on the femur, tibia and patella. Using these jigs as guides, the surgeon removes wafers of bone, approximately 8-10mm thick, from the ends of the femur, tibia and patella using a special bone saw. The cuts have to be accurate (within 2-3 degrees and 1-2mm) for optimal results. Any crookedness or deformity in the knee is corrected during these steps.
As people are of different shapes and sizes, their bones also vary in shape and size. The surgeon sizes the bones during the operation using special measuring tools to choose the appropriate size for that patient. There is a large range of sizes available “on the shelf” that the surgeon uses to custom fit the patient.
The cut ends of femur and tibia bones are capped with artificial prostheses made of special metal alloys such as cobalt chrome and titanium. The prostheses can be attached to the bones by one of two methods. One option is to cement the prostheses to the bone using a special acrylic bone cement. The other option is to use a prosthesis that has pores on it surface and/or a special calcium coating to which the bone will adhere. A flat plastic “cushion” is placed between the metal surfaces to act as a bearing surface. A plastic “button” may also be used to cap the surface of the patella.
The surgeon makes a final check that the knee moves well and the leg is straight. A thin plastic tube may be placed to allow excess blood to drain away. The wound is then closed. A urinary catheter may be inserted.
In traditional TKR, an incision is required that cuts along the length of the quadriceps tendon (a large tendon attached to the lower end of the quadriceps muscle, which makes up the bulk at the front of the thigh). This is the most important muscle of the knee being responsible for all weight bearing activities i.e. walking, rising from a chair, getting in & out of a car, climbing stairs.
More recently using less invasive techniques and special surgical tools, surgeons are able to perform TKR that violates the quadriceps tendon to a lesser degree.
This allows quicker recovery and less pain than the traditional method of TKR.
Additionally, modern methods of anaesthesia and injecting the surgical wound during the operation with long acting local anaesthetic, have significantly decreased the degree of post-operative pain after a TKR.
At the time of the consultation, please let your surgeon know all your regular medications (especially blood thinning tablets such as aspirin, clopidogrel, Plavix and warfarin) and current medical conditions.
One or two weeks before the surgery you will be contacted for a pre-admission clinic appointment at the hospital where you will be having the surgery. At the pre-admission clinic appointment (which takes a couple of hours) you will meet a nurse who will do routine blood tests and an ECG. A physiotherapist will explain to you the exercises you will be doing after the operation and teach you how to use crutches.
On the day before surgery, the hospital will contact you by phone to advise you of the time you need to fast from, and the time to present to the hospital. Most patients will come into the hospital on the day of the surgery.
Please bring with you all your medications, the relevant x-rays as well as other personal belongings that you may need during your hospital stay. The hospital admission forms will give you more information with regard to the kind of items you may want to bring with you.
Your anaesthetist will meet you just before your operation to ask you a few questions about your general health and previous anaesthetics. General anaesthesia or spinal anaesthesia or both can be used. The anaesthetist will discuss with you as to which is most appropriate in your case.
Day of operation: When you wake up in recovery you may notice a drip in your arm, a bandage around your knee, a thin plastic tube draining excess blood from the surgical site and possibly a urinary catheter. You may feel drowsy after the anaesthetic. Most patients feel little or no pain, and will rest in bed on the day of the operation.
Day 1: With the help of a physiotherapist, you may be sitting out of bed and taking a few steps with the aid of a walking frame.
Day 2-4: Some patients after a total knee replacement may already walk with crutches or a walking stick. If your progress is good, the physiotherapist will teach you how to negotiate stairs. Around this time, you may be able to take yourself to the bathroom without assistance.
Day 5-7: If recovery is good, patients often go home after day 5-7. Some patients who are slower in their recovery or who live alone may wish to be transferred to a rehabilitation hospital for additional rehabilitation. Before discharge patients are shown how to self-administer Clexane injections (blood thinning medications to prevent blood clots). These injections are performed using a tiny needle and are not painful. The injections will be for a total of 3 weeks.
|Activities after Total Knee Replacement||Recovery Time|
|Walking frame||1-2 days|
|Walk with crutches or a walking stick||2-4 days|
|Stairs (one step at a time)||2-4 days|
|Rise from chair or toilet by self, using hand-rail.||2-4 days|
|Driving – left knee (automatic car)||2-3 weeks|
|Driving – right knee||4-6 weeks|
|Return to sedentary work||3-6 weeks|
Note: This is a typical recovery after total knee replacement surgery. Time and speed of recovery will vary between individual patients. Before resuming driving, please check with your surgeon.
It is normal to experience some ache in the knee, especially at night, for the first few weeks which may require strong pain-killers. It is normal for the knee to be warm, swollen and stiff for 3-6 weeks after surgery. Some patients may experience pain, swelling and stiffness for a number of months after surgery.
Complication related to the knee include:
There are also complications not specific to knee surgery, that can occur with any other type of operation. These may include anaesthetic complications, allergies, reactions to medications, etc.
Serious complications are uncommon but may occur in approximately 2-3% of cases. The risks are higher in patients with diabetes, severe obesity, age >85yo and those with other serious illnesses.
Please refer to the information pamphlet given to you by the surgeon during your consultation with regard to the procedure and list of other possible complications. If you have any concerns, please discuss with the surgeon.
Knee replacements cannot restore full function of the knee. Most patients lose some flexibility (bending) of the knee, causing difficulty in squatting and kneeling.
Most patients after TKR can expect pain-free walking, reasonable stair climbing, and depending on age and previous level of fitness may be able to participate in low-impact sports such as golf, swimming, cycling and social tennis. Patients may also be able to jog/trot for a few yards, but not run for any significant distances. Sexual activity may be resumed as soon as comfortable.
It is difficult to provide an exact number on an individual basis as there are many complex factors that determine the life span of a knee replacement. However, we do have some data on how long an average knee will last.
According to the National Joint Replacement Registry, when looking at thousands of knee replacements of all types that have been performed in Australia, 5.6% of total knee replacements had to be re-operated/revised (medical term for having to redo a knee for whatever reason) by the 10 year mark. In simple terms, if one hundred patients had total knee replacements, 5.6 patients had to have a redo operation by the time 10 year mark is reached. To put it another way, if 100 patients had total knee replacements, 94.4 patients have not required a redo operation after 10 years.
We do not have results from the Registry what happens to knee replacements after 10 years as the Registry has only been running for approximately 10 years. However, from looking at results from other Registries such as the Swedish Registry, knee replacements start to fail at increasing rates after 10-15 years of service life.
It depends on the sensitivity of the detectors but probably yes. We will be happy to give you a card, stating that you have had a knee replacement, that you can present at the airport.